1. Field of the Invention
The present invention relates to an ultrasound diagnosis apparatus for use in the field of medical treatment, and more particularly to a channel reduction technology.
2. Description of Related Art
Ultrasound diagnosis apparatuses are used in the field of medical treatment for the purpose of diagnosing diseases of a living body (patient). More specifically, ultrasonic diagnosis apparatuses transmit an ultrasonic pulse to a living body and receive a reflected wave therefrom for forming an ultrasonic image based on a receiving signal obtained by the reflected wave received. A typical ultrasonic diagnosis apparatus includes an apparatus body (main unit) and a probe (probe unit) connected to the apparatus body. The probe generally includes a probe head, a cable, and a connector.
An array transducer (transducer array) provided within the probe head is composed of a plurality of transducer elements. There is a recent trend of forming the array transducer by a multiple elements. A variety of 2D array transducers which effect two-dimensional scanning of an ultrasonic wave to form a three dimensional space are put into practical use. Among them are 2D array transducers including several thousand transducer elements.
When a signal line is provided independently for each of the transducer elements forming an array transducer, a great number of signal lines must be connected for the array transducer as a whole. In such a structure, the diameter of a probe cable (a cable which encases a plurality of signal lines) extended from the probe head becomes very large, and the number of terminals (pins) of the connector provided at the end of the probe cable is also increased. In addition, because it is necessary to provide a transmitter and a receiver for each transducer element, the transmitter section and the receiver section will have an increased circuit scale. Accordingly, with the development of array transducers including multiple transducer elements, there has been a demand that the diameter of the probe cable and the number of channels (the number of transmitters and receivers) both be reduced.
Japanese Patent Laid-Open Publication No. 2001-104303 discloses a structure in which a plurality of transducer elements are fixedly connected to a single common signal line (See FIGS. 2 and 4 of the publication). Japanese Patent Laid-Open Publication No. 2001-276064 discloses a structure in which two phase-adjusting and summing circuits (or beam forming circuits) are provided in stages. Japanese Patent Laid-Open Publication No. Hei 9-322896 discloses, in FIG. 6, that a plurality of groups are fixedly set for a 2D array transducer, that a plurality of first beam formers are connected to the plurality of groups, and that a plurality of second beam formers are provided at the subsequent stage of the plurality of first beam formers. None of these documents, however, describes that a plurality of groups are dynamically set for each of sub arrays provided on the 2D array transducer, or that channel reduction is performed using each of these groups. U.S. Pat. No. 5,832,923 discloses that a plurality of 2D sub arrays are defined on a 2D array transducer and that a plurality of groups are defined on each sub array. In this patent, however, the number of transducer elements forming each group is identical among a plurality of groups. Accordingly, this document does not describe the feature of varying the number of transducer elements forming each group in accordance with the beam direction.